Currently, a commercial process to apply swatches to a sheet, such as shown in Lerner, et al., U.S. Pat. No. 4,061,521, provides a relatively high speed operation (e.g., 4,500 sheets per hour) in which blank sheets are fed continuously through operating stations including an adhesive applying station and one or more swatch applying station where swatches are applied to the sheet.
Blank sheets are pushed by feed fingers through the adhesive applying station and the swatch applying stations on top of travel surfaces, at least some of which include upstanding guide portions on one side thereof. These side sheet guides are spaced apart a distance corresponding to the width of the sheet to ensure the sheets maintain proper alignment as they are pushed by the feed fingers through the adhesive applying station and the swatch applying stations. Multiple side sheet guides are required throughout the swatch applying machinery to maintain the sheets in proper alignment. Side sheet guides must be placed before and after the adhesive applying station and each swatch applying station to keep the sheets aligned as they are pushed between stations. Because the sheets are pushed at their trailing edges by the feed fingers, without the sheet guides, the sheets may skew sideways, resulting in misfeeds and/or sheets having misaligned swatches thereon.
The feed fingers that push the sheets along the travel surfaces are attached to conveyors in the form of drive chains. Separate drive chain conveyors extend between each of the operating stations so that several sets of feed fingers will have pushed the sheets during their travel from the infeed to the outfeed of the sheets from the machine. The use of multiple sets of conveyers and multiple sets of feed fingers to push each sheet to and from each operating station requires precise coordination of the timing of the positions of each set of feed fingers on each conveyor to push the sheet through the operating stations, particularly where operating speed is maximized. Further, the coordination necessary to push a sheet to an operating station with a first set of feed fingers on a first conveyor and then to have a second set of feed fingers on a second conveyor positioned to push the sheet from the operating station must be precisely timed because errors in the coordination could result in misfeeds or misprinted sheets, requiring the machinery to be stopped to correct the errors and reducing the production efficiency of the machinery.
The feed fingers do not positively grip the sheets. As there is no positive gripping, the feed fingers extend a relatively high distance above the travel surfaces to ensure that they contact the rearward edge of the sheets as occasionally the sheets will not be lying flat on the travel surfaces such as if the rearward edge of the sheet curls.
Because of the height that the feed fingers extend above the travel surfaces and the lack of positive gripping of the sheets, the feed fingers are not able to push the sheets through the stations. More specifically, upper and lower rollers cooperate to form nips of the operating stations into which the sheets are fed and from which they are discharged. In the nips, adhesive and swatches are applied to the sheets. The height of the feed fingers does not allow for their passage through the nip areas between the closely spaced rollers of the operating stations.
Accordingly, instead of using a single set of feed fingers to push the sheets through each operating station, a separate set of feed fingers pushes each of the sheets to each station. The nip formed by the rollers in each station draw the sheets therethrough and discharges them downstream to the next conveyor at which point another set of feed fingers then pushes the sheets to the next station. The timing of the multiple sets of feed fingers must be coordinated so that as a sheet leaves a station a new set of feed fingers are positioned to push the sheet to the next station. If the timing is not correctly coordinated, misfeeds may occur. Misfeeds are undesirable because the swatch applying machinery must be stopped while the misfed sheet or sheets are removed and the machinery reset for continued operation.
The swatch applying machinery can accommodate sheets of different sizes. When a different size of sheet is fed through the swatch applying machinery, each side sheet guide and associated travel surface must be readjusted to maintain the different size of sheet in proper alignment as it travels through the adhesive applying station and the swatch applying stations. Readjusting each side sheet guide in the swatch applying machinery is labor intensive. The time required to properly readjust each side sheet guide when changing the size of the sheet can be as much as four hours. In addition to the costs associated with the labor involved in readjusting the side sheet guides, the swatch applying machine must sit idle during this time.
As sheets are fed through the swatch applying machinery at higher speeds, the sheets have a tendency to float above the travel surfaces. At higher speeds, the front or leading edge of the sheet tends to lift up, allowing air to flow underneath the sheet. The result is a sheet that is partially floating on air. The faster the swatch applying machinery is run, i.e., the more sheets per hour fed through the machine, the greater the tendency for the sheets to float. The problem of sheet float is particularly acute when lighter sheet stocks are used. The use of lighter sheet stock tends to increase the tendency for the sheets to lift up from the travel surfaces because the sheets do not have sufficient weight to maintain themselves in a planar alignment and against the travel surfaces. When sheets float, there are increased occurrences of misfeeds and misprints. Floating sheets tend to deviate from their preferred alignment, even with the assistance of the side sheet guides associated with the travel surfaces. The corners of floating sheets tend to catch on various parts of the swatch applying machinery, causing the sheets to become misaligned.
The problem of floating sheets limits the operating speed of swatch applying machinery. The operating speed of the swatch applying machinery must be reduced below optimal levels to attempt to minimize the occurrence of sheet float. Every time a floating sheet causes a misfeed or misprint, the swatch applying machinery must be stopped, the offending sheet removed, and the machinery reset for continued production. The problem of floating sheets is costly. Labor must be expended to remove sheets that result in misfeeds or misprints. Labor must also be expended to reset the swatch applying machinery for continued production. The time that the swatch applying machinery must remain idle while offending sheets are removed and the machinery reset is costly in terms of lost production time.
Various attempts to reduce the problem of sheet float have been attempted with limited success. The swatch applying machinery may be run at lower speeds. Although this solution may be effective at addressing sheet float, it is desirable to operate the swatch applying machinery at higher speeds to increase production of finished sheets with applied swatches. Another attempt at reducing the occurrence of sheet float involves placing sheet hold-down guides throughout the swatch applying machinery. Sheet hold-down guides may be placed between the stations to help maintain the sheets in contact with the travel surfaces. Although sheet hold-down guides help address the problem of sheet float, because the leading edges of the sheets may still lift up from the travel surfaces during high speed operation of the machinery during the time they are not being held down by the guides against the travel surfaces.
Accordingly, a method and apparatus are needed for directing a sheet through swatch applying machinery that reduce the setup time required for changing sheet sizes, reduce problems associated with the occurrence of sheet float, and which allow for higher speed operation of the swatch applying machinery and thus more efficient and increased production rates of sheets with swatches applied thereon.